Semiconductor integrated circuit device

ABSTRACT

With a high-speed nonvolatile phase change memory, reliability in respect of the number of refresh times is enhanced. In a memory cell forming area of a phase change memory using a MISFET as a transistor for selection of memory cells, a phase change material layer of a memory cell comprising a resistor element, using a phase change material, is formed for common use. As a result, variation in shape and a change in composition of the phase change material, caused by isolation of memory cell elements by etching, are reduced, thereby enhancing reliability of memory cells, in respect of the number of refresh times.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor integrated circuitdevice, and in particular, to technology effective for application to asemiconductor integrated circuit device having a high density integratedmemory circuit formed of a phase change material, a memory combined witha logic wherein a memory circuit and a logic circuit are provided on thesame semiconductor substrate, or an analog circuit.

2. Description of The Related Art

With a memory combined with a logic, wherein a memory (phase changememory) using a resistor element made of, for example, a phase changematerial, and a logic circuit made up of MISFETs (Metal InsulatorSemiconductor Field Effect Transistors), and so forth, are provided onthe same semiconductor substrate, all or parts of memory cell elementsadjacent to each other are formed by dividing the phase change materialin, for example, an etching process. Further, a bit line contactelectrode for electrically connecting a bit line for use in designatingan address of each of the memory cell elements with an active area on asemiconductor substrate of each of the MISFETs is disposed between theresistor elements making up respective memory cells. One related to thistype of device has been disclosed in, for example, Japanese PatentLaid-open No. 2002-540605. Further, a memory cell with a structure usinga diode as a selection element by having a plate electrode made of aphase change memory material, for common use, has been disclosed (referto, for example, Japanese Patent Laid-open No. 1993-21740, and JapanesePatent Laid-open No. 2003-100084). Still further, a memory cell with astructure using a transistor as a selection element by having a plateelectrode made of a phase change memory material, for common use, hasbeen disclosed (refer to, for example, Japanese Patent Laid-open No.2003-100991).

With a process technology for isolating resistor elements from eachother for every memory cell, the isolated surfaces of the phase changematerial change in characteristics. First, the isolated surfaces of thephase change material come into contact with a different material suchas, for example, an inter-level insulation film, and so forth. Also, inthe case of the resistor elements being isolated from each other byetching, memory cell elements vary in shape. Further, portions of thephase change material, exposed due to isolation, change in composition.

As a result, a problem has arisen in that deterioration occurs toreliability in respect of the number of refresh times of a phase changememory, for use in a highly integrated memory circuit and the memorycombined with the logic, of which uniformity in electricalcharacteristics is required.

Further, in the case of technology whereby a bit line plug is disposedbetween memory cell elements, a limitation is imposed on disposition ofthe memory cell elements by the bit line plug.

As a result, a problem has been encountered that a limitation is imposedon integration of memory cells.

Furthermore, in the case of a phase change memory technology using aMISFET as a selection switch, memory cell lower contact electrodesconnected to a phase change memory differ in shape from contactelectrodes not connected to the phase change memory in order to achievehigher performance of the phase change memory.

As a result, a problem has arisen in that a process technology for usein the memory combined with the logic becomes complicated, resulting inhigher cost.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a technologycapable of enhancing reliability of memory cell elements using a phasechange material, of which uniformity in electrical characteristics isrequired, particularly, in a semiconductor integrated circuit devicehaving, for example, a high density integrated memory circuit formed ofa phase change material, a memory combined with a logic wherein a memorycircuit and a logic circuit are provided on the same semiconductorsubstrate, or an analog circuit.

Another object of the invention is to achieve higher integration of asemiconductor integrated circuit device.

Still another object of the invention is to achieve higher performanceof the semiconductor integrated circuit device.

A further object of the invention is to achieve reduction in cost.

The above and other objects and features of the invention will beapparent from the following description of the disclosure and theaccompanying drawings.

A summary of representative embodiments of the invention as disclosed bythe present application is broadly described as follows.

In a memory cell area where resistor elements of a phase change memoryare disposed so as to be integrated, a phase change material layer isfor common use, and a memory cell upper plate electrode for common use,to be connected to a power source line, is formed in the upper layer ofthe phase change material layer. As a result, exposure of the phasechange material layer is eliminated except for the memory cellspositioned at the outermost peripheral parts of the memory cell area,and effects of etching on the shapes of the memory cell elements andvariation in the composition thereof is eliminated, so that electricalcharacteristics of the memory cell elements become uniform, therebyenabling reliability thereof to be enhanced.

Further, a distance between sidewalls of the phase change materiallayer, formed for isolating the memory cell elements positioned at theoutermost peripheral parts of an array area from a directly peripheralcircuit of a memory adjacent thereto or a logic circuit area and soforth, by etching, is rendered still longer. Or a dummy pattern isdisposed on the periphery of the memory cell elements positioned at theoutermost peripheral parts of the array area. By this arrangement,effects of exposed parts of the sidewalls of the phase change materiallayer can be suppressed without changing a high degree of integration ofa memory.

Further, memory operation is executed by turning the initial conditionof the resistor elements as a whole into a high resistance conditionwhile turning a portion of the phase change material layer into a lowresistance condition. As a result, interaction between the memory cellelements in a low resistance condition can be suppressed.

Furthermore, in the phase change memory wherein the phase changematerial layer is for common use in the array area where the memory cellelements are disposed so as to be integrated, and the memory cell upperplate electrode for common use, to be connected to the power sourceline, is formed in the upper layer of the phase change material layer,bit lines are disposed under phase change recording material films. As aresult, bit line plugs can be formed without penetrating through thephase change material layer, and the memory cell upper plate electrode,so that the side walls of the phase change material layer are preventedfrom exposure due to penetration by the bit line plugs.

Still further, in the phase change memory wherein the phase changematerial layer is for common use in the memory cell area where thememory cell elements are disposed so as to be integrated, and the memorycell upper plate electrode for common use, to be connected to the powersource line, is formed in the upper layer of the phase change materiallayer, a high resistive conductive material, such as a material selectedfrom the group consisting of TiN, TiAlN, and PolySi, only in the upperpart of the memory cell lower contact electrodes, respectively.

As a result, the upper part of each of the memory cell lower contactelectrodes acts as a heater generating Joule heat, and a phase changearea of the phase change material layer, particularly, the phase changearea in close proximity to a contact part between the plugs for thephase change memory and the phase change material layer can be changedinto a desired shape.

Further, with the phase change memory, the high resistive conductivematerial is disposed only in the upper part of each of the memory celllower contact electrodes connecting the phase change material layer tocontact electrodes connected with respective active areas on thesemiconductor substrate, for the MISFETs. As a result, while optimizingthe memory cell lower contact electrode for enhancement incharacteristics of the phase change memory, the contact electrodes,connected with the respective respective active areas on thesemiconductor substrate for the MISFETs, along with bit line contactelectrodes, can be concurrently formed, thereby enabling cost reduction.

Further, the phase change material layer is formed so as to a stackedlayer made up of high-melting phase change material film and low-meltingphase change material film. As a result, the shape of a phase changearea of the phase change material layer can be caused to change into adesired shape along a direction in which the phase change material filmsare stacked.

Still further, a memory array is formed by use of the memory cell upperplate electrode sharing a plurality of the resistor elements. As aresult, it is possible to suppress interaction between the memory cellelements due to operation of word lines and bit lines, designating anaddress of each of the memory cell elements while the memory cell ishighly integrated.

Yet further, the phase change material layer is formed above the bitlines. As a result, the memory cell elements can be disposed withoutbeing affected by disposition of the bit lines and bit line contactelectrodes.

Further, with the phase change memory wherein the phase change materiallayer is formed above the bit lines, the resistor elements are formed bydividing the phase change material layer. As a result, the resistorelements as divided can be disposed without being affected by thedisposition of the bit line contact electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the principal parts of Embodiment 1 of asemiconductor integrated circuit device according to the invention;

FIG. 2 is a layout view of the principal parts of the semiconductorintegrated circuit device shown in FIG. 1;

FIG. 3 is another layout view of the principal parts of thesemiconductor integrated circuit device shown in FIG. 1;

FIG. 4 is a sectional view of the principal parts of a substrate of thesemiconductor integrated circuit device shown in FIG. 1 during afabrication process;

FIG. 5 is another sectional view of the principal parts of the substrateof the semiconductor integrated circuit device shown in FIG. 1 duringthe fabrication process;

FIG. 6 is still another sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 7 is a further sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 8 is a still further sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 9 is a yet further sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 10 is another sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 11 is still another sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 12 is a further sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 13 is a still further sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 14 is a yet further sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 15 is another sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 16 is still another sectional view of the principal parts of thesubstrate of the semiconductor integrated circuit device shown in FIG. 1during the fabrication process;

FIG. 17 is another sectional view of the principal parts of Embodiment 1of the semiconductor integrated circuit device according to theinvention;

FIG. 18 is still another layout view of the principal parts ofEmbodiment 1 of the semiconductor integrated circuit device according tothe invention;

FIG. 19 is a further layout view of the principal parts of Embodiment 1of the semiconductor integrated circuit device according to theinvention;

FIG. 20 is a still further layout view of the principal parts ofEmbodiment 1 of the semiconductor integrated circuit device according tothe invention;

FIG. 21 is a yet further layout view of the principal parts ofEmbodiment 1 of the semiconductor integrated circuit device according tothe invention;

FIG. 22 is another layout view of the principal parts of Embodiment 1 ofthe semiconductor integrated circuit device according to the invention;

FIG. 23 is still another layout view of the principal parts ofEmbodiment 1 of the semiconductor integrated circuit device according tothe invention;

FIG. 24 is a further layout view of the principal parts of Embodiment 1of the semiconductor integrated circuit device according to theinvention;

FIG. 25 is a sectional view of the principal parts of a substrate ofEmbodiment 2 of a semiconductor integrated circuit device according tothe invention during a fabrication process;

FIG. 26 is a sectional view of the principal parts of Embodiment 2 ofthe semiconductor integrated circuit device according to the invention;

FIG. 27 is another layout view of the principal parts of Embodiment 1 ofthe semiconductor integrated circuit device according to the invention;

FIG. 28 is a layout view of the principal parts of Embodiment 2 of thesemiconductor integrated circuit device according to the invention;

FIG. 29 is another layout view of the principal parts of Embodiment 2 ofthe semiconductor integrated circuit device according to the invention;

FIG. 30 is still another layout view of the principal parts ofEmbodiment 2 of the semiconductor integrated circuit device according tothe invention;

FIG. 31 is a further layout view of the principal parts of Embodiment 2of the semiconductor integrated circuit device according to theinvention;

FIG. 32 is a sectional view of the principal parts of a substrate ofEmbodiment 3 of a semiconductor integrated circuit device according tothe invention during a fabrication process;

FIG. 33 is another sectional view of the principal parts of thesubstrate of Embodiment 3 of the semiconductor integrated circuit deviceaccording to the invention during the fabrication process;

FIG. 34 is still another sectional view of the principal parts of thesubstrate of Embodiment 3 of the semiconductor integrated circuit deviceaccording to the invention during the fabrication process;

FIG. 35 is a further sectional view of the principal parts of thesubstrate of Embodiment 3 of the semiconductor integrated circuit deviceaccording to the invention during the fabrication process;

FIG. 36 is a still further sectional view of the principal parts of thesubstrate of Embodiment 3 of the semiconductor integrated circuit deviceaccording to the invention during the fabrication process;

FIG. 37 is a yet further sectional view of the principal parts of thesubstrate of Embodiment 3 of the semiconductor integrated circuit deviceaccording to the invention during the fabrication process;

FIG. 38 is a sectional view of the principal parts of the substrate ofEmbodiment 3 of the semiconductor integrated circuit device according tothe invention;

FIG. 39 is a sectional view showing the principal parts of thesemiconductor integrated circuit device, for describing an advantageouseffect of the invention;

FIG. 40 is another sectional view showing the principal parts of thesemiconductor integrated circuit device, for describing the advantageouseffect of the invention;

FIG. 41 is still another sectional view showing the principal parts ofthe semiconductor integrated circuit device, for describing theadvantageous effect of the invention;

FIG. 42 is a further sectional view showing the principal parts of thesemiconductor integrated circuit device, for describing the advantageouseffect of the invention;

FIG. 43 is a still further sectional view showing the principal parts ofthe semiconductor integrated circuit device, for describing theadvantageous effect of the invention;

FIG. 44 is a yet further sectional view showing the principal parts ofthe semiconductor integrated circuit device, for describing theadvantageous effect of the invention;

FIG. 45 is a sectional view of the principal parts of another substrateof Embodiment 2 of the semiconductor integrated circuit device accordingto the invention;

FIG. 46 is a layout view of the principal parts of Embodiment 3 of thesemiconductor integrated circuit device according to the invention;

FIG. 47 is another layout view of the principal parts of Embodiment 3 ofthe semiconductor integrated circuit device according to the invention;

FIG. 48 is a sectional view of the principal parts of a conventionalsemiconductor integrated circuit device;

FIG. 49 is a sectional view of the principal parts of Embodiment 4 of asemiconductor integrated circuit device according to the invention;

FIG. 50 is a layout view of the principal parts of Embodiment 4 of thesemiconductor integrated circuit device according to the invention; and

FIG. 51 is another layout view of the principal parts of Embodiment 4 ofthe semiconductor integrated circuit device according to the invention.

DETAILED DESCRPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention are described in detail hereinafter withreference to the accompanying drawings. In all figures for describingthe respective embodiments, parts having the same function are denotedby like reference numerals, omitting repeated description thereof.

<Embodiment 1>

FIG. 1 is a sectional view of the principal parts of Embodiment 1 of asemiconductor integrated circuit device according to the invention. FIG.1 shows a sectional view of a logic circuit area of a logic as well as amemory cell area of a phase change memory cell of a memory combined witha logic, and among the areas shown in FIG. 1, reference numeral lgcdenotes the logic circuit area. In the logic circuit area lgc, ann-channel MISFET QN is formed. The n-channel MISFET QN has semiconductorareas DN formed in the upper parts of a p-well 2 so as to be isolatedfrom each other, making up a LDD (Lightly Doped Drain) structure, a gateinsulation film 4 formed on top of a semiconductor substrate 1, and agate electrode GN formed on top of the gate insulation film 4.

In the logic circuit area lgc, a p-channel MISFET QP is formed. Thep-channel MISFET QP has semiconductor areas DP formed in the upper partsof an n-well 2 a so as to be isolated from each other, making up a LDD(Lightly Doped Drain) structure, a gate insulation film 4 formed on topof the semiconductor substrate 1, and a gate electrode GP formed on topof the gate insulation film 4.

The n-channel MISFET QN and the p-channel MISFET QP are isolated fromeach other with an isolation area 3 a of a shallow-groove embedded type,interposed therebetween.

In the logic circuit area, the logic circuit area of the logic, a senseamplifier of the memory cell, and so forth are disposed.

Further, a memory cell area mmry where the phase change memory cell isformed is positioned. In the memory cell area, for example, n-channelMISFETs QM for selection of the memory cell are formed. The n-channelMISFETs QM for selection of the memory cell are formed in the upperparts of the p-well 2 so as to be isolated from each other, each havingsemiconductor areas DN, and DNC, making up a LDD (Lightly Doped Drain)structure, a gate insulation film 4 formed on top of the semiconductorsubstrate 1, and a gate electrode GN formed on top of the gateinsulation film 4. The semiconductor area DNC is shared by the n-channelMISFETs for selection of the memory cell, adjacent to each other, formedin the same element active area.

The n-channel MISFETs QM for selection of the memory cell, p-channelMISFET QP, and n-channel MISFET QN are covered with inter-levelinsulation films, 11 a, 11 b, deposited on top of the semiconductorsubstrate 1.

The inter-level insulation films 11 a, 11 b are made up of, for example,a silicon oxide film, respectively, by, for example, the public knownplasma enhanced CVD process, and so forth. The upper surface of theinter-level insulation film 11 b is planarized such that a height of theinter-level insulation film 11 b in the memory cell are a substantiallymatches that in the logic circuit area.

In the semiconductor area DNC of the memory cell area mmry, a bit linecontact electrode BC made up of a barrier metal film 12 and a tungstenfilm 13 is formed.

The bit line contact electrode BC is electrically connected to the areaDNC shared by the n-channel MISFETs QM1, QM2 for selection of the memorycell.

In the respective semiconductor areas DN of the memory cell area mmry, ametal contact electrode CT made up of a barrier metal film 14 and atungsten film 15 is formed. The n-channel MISFETs QM1, QM2, forselection of the memory cell, and the respective semiconductor areas DNthereof are electrically connected with the metal contact electrode CT.In the semiconductor area DP of the logic circuit area, a metal contactelectrode CT made up of a barrier metal film 14 and a tungsten film 15is formed. The metal contact electrode CT is electrically connected withthe semiconductor area DP of the p-channel MISFET QP.

In the semiconductor area DN of the logic circuit area, a metal contactelectrode CT made up of a barrier metal film 14 and a tungsten film 15is formed. The metal contact electrode CT is electrically connected withthe semiconductor area DN of the n-channel MISFET QN.

An inter-level insulation film 11 c is deposited on top of theinter-level insulation film 11 b. The inter-level insulation film 11 cis made up of, for example, a silicon oxide film and is formed by, forexample, the public known plasma enhanced CVD process, and so forth.

In the inter-level insulation film 11 c, a bit line BL and a first layerinterconnect M1 are formed. The bit line BL is formed by depositing abarrier metal film 16, made up of, for example, a titanium film and atitanium nitride film, and a tungsten film 17 in that order from a lowerlayer. The bit line BL is electrically connected with the bit linecontact electrode BC, and is further electrically connected with thesemiconductor area DNC of the n-channel MISFET QM for selection of thememory cell through the intermediary of the bit line contact electrodeBC.

The first layer interconnect M1 of the logic circuit area is formed bydepositing a barrier metal 16 a made up of, for example, a titanium filmand a titanium nitride film, and a tungsten film 17 a in that order froma lower layer. The first layer interconnect M1 is electrically connectedwith the metal contact electrode CT, and is further electricallyconnected with the semiconductor area DP of the p-channel MISFET QP andthe semiconductor area DN of the n-channel MISFET QN through theintermediary of the metal contact electrode CT.

An inter-level insulation film 11 d is deposited on the upper surface ofthe inter-level insulation film 11 c. The inter-level insulation film 11d is made of, for example, silicon oxide. The upper surface of theinter-level insulation film 11 d is planarized such that a height of theinter-level insulation film 11 d in the memory cell area mmrysubstantially matches that in the logic circuit area lgc.

In the inter-level insulation film 11 d of the memory cell area mmry,contact holes for exposing the top of the metal contact electrodes CT,respectively, are bored.

In the respective contact holes, a spacer insulation film 18 made of,for example, silicon nitride or silicon oxide, and a conductive material19 made of, for example, tungsten are embedded, and further, on topthereof, a high resistive conductive material 20 made of, for example,titanium nitride is embedded.

A memory cell lower contact electrode TP is electrically connected withthe metal contact electrodes CT, and is further electrically connectedwith the respective semiconductor areas DN of the n-channel MISFETs QNfor selection of the memory cell through the intermediary of therespective metal contact electrodes CT. That is, the memory cell lowercontact electrodes TP and each of the metal contact electrodes CT makeup a two-stage plug electrode.

An inter-level insulation film 11 e is deposited on the upper surface ofthe inter-level insulation film 11 d. The inter-level insulation film 11e is made of, for example, silicon oxide.

In the inter-level insulation film 11 e of the memory cell area mmry, aresistor element R serving as a memory element is formed.

The resistor element R is formed in a plate-like shape, and comprises aphase-shift-material-peel-preventive film 21 made of, for example,silicon nitride, a phase change material layer CG made up of a phasechange recording material film 22 covering the surface of thephase-shift-material-peel-preventive film 21, and, for example, a phasechange recording material film 23 differing from the phase changerecording material film 22, and a memory cell upper plate electrode 24made of, for example, of tungsten, covering the surface of the phasechange material layer CG

The phase change recording material films 22, 23, making up the phasechange material layer CG are made of, for example, chalcogenideGe₂Sb₂Te₅, or Ge₃Sb₂Te₆.

The lower part of the resistor element R is electrically connected withthe memory cell lower contact electrode TP, and is electricallyconnected with the respective semiconductor areas DN of the n-channelMISFETs QM for selection of the memory cell through the intermediary ofthe memory cell lower contact electrode TP.

The resistor element R is formed in such a way as to cover a pluralityof the memory cell lower contact electrodes TP each corresponding to aunit bit of the memory cell.

In the inter-level insulation film 11 e of the memory cell area mmry, acontact hole for exposing a portion of the upper surface of the memorycell upper plate electrode 24 is bored. In the contact hole, a barriermetal film 25 made up of, for example, a titanium film and a titaniumnitride film is embedded and further, a metal film 26 made of tungstenis embedded therein, forming a via VM in a memory cell area.

In the inter-level insulation films 11 d, 11 e of the logic circuit arealgc, a contact hole for exposing a portion of the upper surface of thefirst layer interconnect M1 is bored. In the contact hole, a barriermetal film 25 a made up of, for example, a titanium film and a titaniumnitride film is embedded and further, a metal film 26 a made of tungstenis embedded therein, forming a via VL in a logic circuit area.

The upper surface of the inter-level insulation film 11 e is planarizedsuch that a height of the inter-level insulation film 11 e in the memorycell area mmry substantially matches that in the logic circuit area lgc.

An inter-level insulation film 11 f is deposited on top of theinter-level insulation film 11 e. The inter-level insulation film 11 fis made of, for example, silicon oxide. In the inter-level insulationfilm 11 f, a second layer interconnect M2 is formed.

Now, a layout of the principal parts of the memory cell area accordingto Embodiment 1 is described with reference to FIGS. 2 and 3.

First, as shown in FIG. 2, active areas (element active areas or elementforming areas) L of the n-channel MISFETs, each having the gateelectrodes GN, are formed over the p-well 2. These gate electrodes GNare used as word lines of a memory cell array.

Further, the metal contact electrodes CT are formed on the respectiveactive areas L of these n-channel MISFETs.

Furthermore, the bit line contact electrode BC is formed on therespective active areas L of these n-channel MISFETs. The bit linecontact electrodes BC are formed so as to be protruded along they-direction of the respective active areas L of the n-channel MISFETs.

Further, as shown in FIG. 3, the respective bit lines BL are disposed soas to come into contact with the upper part of a portion of each of thebit line contact electrodes BC, protruded in the y-direction of therespective active areas L of the n-channel MISFETs.

Further, the respective memory cell lower contact electrodes TP areformed on respective tops of the metal contact electrodes CT (notshown).

Still further, the phase change material layer CG is formed across theplane of a layout view of the principal parts, shown in FIGS. 2 and 3,respectively. The phase change material layer CG is connected with thememory cell lower contact electrodes TP and the memory cell upper plateelectrode 24.

Needless to say, the active areas L, shown in FIGS. 2 and 3,respectively, are disposed with a periodicity.

Further, needless to say, the gate electrodes GN for use as therespective word lines, shown in FIGS. 2 and 3, respectively, areparallel to each other and continuous in the memory cell area, that is,are disposed along the x-direction.

Furthermore, needless to say, the respective bit lines shown in FIGS. 2and 3, respectively, are parallel to each other and continuous in thememory cell area, that is, are disposed along the y-direction.

As shown in FIG. 3, the present embodiment is characterized in that therespective metal contact electrodes CT are disposed between the bitlines BL adjacent to each other in a plane layout.

Now, the semiconductor integrated circuit device according to Embodiment1 of the invention is described in detail with reference to FIGS. 4 to17 while following steps of a fabrication process thereof. In allfigures for describing the present embodiment, parts having the samefunction are denoted by like reference numerals, omitting repeateddescription thereof.

First, the MISFETs are formed by the public known process. Thesemiconductor substrate 1 is made of monocrystalline silicon of ap-typed conductivity. Further, by use of the public known process, thep-well 2 is formed in the logic circuit area lgc as well as the memorycell area mmry of the semiconductor substrate 1. Furthermore, the n-well2 a is formed in the logic circuit area lgc of the semiconductorsubstrate 1.

In the upper layer of the semiconductor substrate 1 as described above,the isolation areas 3, 3 a, 3 b, of the shallow-groove embedded type areformed by the public known process. Areas defined by the isolation areas(insulation films 3, 3 a, 3 b), respectively, are the so-called activeareas, and in respective portions thereof, elements and so forth areformed. The gate insulation films 4 on the semiconductor substrate 1 aremade of, for example, silicon nitride, and are set to have a thicknessin a range of, for example, on the order of 1.5 to 10 nm.

Subsequently, by use of the public known process, an n-typedpolycrystalline silicon film 5 and a p-typed polycrystalline siliconfilm 5 a are formed. Then, by use of the public known process, LDDactive areas 9 of the n-channel MISFETs, respectively, and LDD activeareas 9 a of the p-channel MISFET, respectively, are formed. Thereafter,by use of the public known process, sidewall spacers 7, made up of, for,example, a silicon oxide film, and sidewall spacers 8, made up of for,example, a silicon nitride film, are formed. Subsequently, by use of thepublic known process, active areas 10 of the n-channel MISFETs,respectively, as well as active areas 10 a of the p-channel MISFET, andn-typed polycide films 6 as well as a p-typed polycide film 6 a areformed. Then, by use of the public know process, inter-level insulationfilms 11 a, 11 b are formed.

Thus, with the MISFETs, the polycide gate electrode structures GN, GP,the diffusion layer areas DN, DNC, DP, the sidewall spacers 7, 8, theinter-level insulation films, 11 a, 11 b are formed by use of the publicknown processes, respectively. The upper surface of the inter-levelinsulation film 11 b is planarized such that a height thereof in thememory cell area substantially matches that in the logic circuit area asshown in FIG. 4.

Subsequently, a photo resist for the formation of the contact holes inthe logic circuit area, the contact holes in the memory cell area, andholes for bit lines in the memory cell area is formed on top of theinter-level insulation film 11 b, and by use of the photo resist as anetching mask, the contact holes are bored in the inter-level insulationfilms, 11 a, 11 b, respectively, so as to expose the respective uppersurfaces of the semiconductor areas DN of the n-channel MISFET QN, thesemiconductor areas DP of the p-channel MISFET QP, semiconductor area DNof the n-channel MISFETs QM for selection of the memory cell,respectively, and semiconductor area DNC for both the n-channel MISFETsQM for selection of the memory cell.

Subsequently, after the removal of a photo resist pattern, the barriermetal film 14 made up of, for example, a titanium film and a titaniumnitride film is deposited in that order from a lower layer on thesemiconductor areas DN, DP, DNC, by a sputtering process, and so forth.On top of stacked films, for example, a tungsten film 15 is stacked by aCVD process, and so forth, to be embedded in the respective contactholes, thereby forming the metal contact electrodes CT, and the bit linecontact electrodes BC. Then, the metal contact electrodes CT, and thebit line contact electrodes BC are etched back until the upper part ofthe inter-level insulation film 11 b is exposed such that the respectiveheights of the metal contact electrodes CT in the respective contactholes matches those of the bit line contact electrodes BC in the contactholes, thereby completely isolating the respective metal contactelectrodes CT and the bit line contact electrodes BC from each other,whereupon a structure as shown in FIG. 5 is formed.

Thereafter, an insulation film made of, for example, silicon nitride isdeposited (not shown) on the entire surface for use as an etch backstopper for the inter-level insulation film 11 b.

Subsequently, after depositing the inter-level insulation film 11 c,made of, for example, silicon oxide, on the semiconductor substrate 1, aphoto resist for the formation of the first layer interconnect for thelogic circuit and the bit lines is formed on top of the inter-levelinsulation film 11 c, and by use of the photo resist as an etching mask,first layer interconnect grooves for the logic circuit and bit linegrooves, exposing portions of the upper surface of the inter-levelinsulation film 11 b, are formed.

Subsequently, the barrier metal film 16, made up of, for example, thetitanium film and titanium nitride film, is deposited in that order fromthe lower layer by the sputtering process and so forth, the tungstenfilm 17 is stacked thereon by the CVD process, and so forth, to form aconductive film, and the conductive film is etched back until the uppersurface of the inter-level insulation film 11 c is exposed and theheight of the upper surface of the bit line BL in the respective groovesmatches that of the first layer interconnect M1 in the respectivegrooves, thereby completely isolating the respective bit lines BL andthe respective first layer interconnects M1 from each other, whereupon astructure as shown in FIG. 6 is formed.

Thereafter, the inter-level insulation film 11 d made of, for example,silicon oxide is deposited on the surface, and subsequently, thephase-shift-material-peel-preventive film 21 made of, for example,silicon nitride is deposited thereon, whereupon a structure as shown inFIG. 7 is formed.

Subsequently, the contact hole in the upper portion of each of thetwo-stage plug electrodes in the memory cell area, exposing the uppersurface of the metal contact electrodes CT in the lower portion of eachof the two-stage plug electrodes, is formed by lithographic and dryetching processes, and the spacer insulation film 18 made of, forexample, silicon nitride is deposited on the entire surface, whereupon astructure as shown in FIG. 8 is formed.

Thereafter, anisotropic etch back is applied to the spacer insulationfilm 18, thereby exposing the upper surface of the metal contactelectrodes CT, whereupon a structure as shown in FIG. 9 is formed.

Subsequently, the barrier metal film (not shown), made up of, forexample, the titanium film and titanium nitride film, is deposited inthat order from a lower layer by the sputtering process and so forth. Ona stacked film, the conductive material 19 made of, for example,tungsten is stacked by the CVD process and so forth to be embedded inthe contact holes, and the conductive material 19 is etched back by useof the public known CMP process until the upper surface of thephase-shift-material-peel-preventive film 21 is exposed and the uppersurface of the conductive material 19 in the respective contact holes isflush with the upper surface of the phase-shift-material-peel-preventivefilm 21, thereby completely isolating the respective conductivematerials 19 from each other, whereupon a structure as shown in FIG. 10is formed.

Thereafter, the conductive material 19 in the respective contact holesis etched back by, for example, 20 nm, whereupon a structure as shown inFIG. 11 is formed.

Subsequently, a high resistive metal film 20, made up of, for example, atitanium film and titanium nitride film, is deposited in that order froma lower layer by the sputtering process and so forth, to be embedded inthe respective contact holes. Then, the high resistive metal film 20 isetched back until the upper surfaces of the memory cell lower contactelectrodes TP are flush with the upper surface of thephase-shift-material-peel-preventive film 21, thereby completelyisolating the respective memory cell lower contact electrodes TP fromeach other, whereupon a structure as shown in FIG. 12 is formed.

Further, with the present embodiment, the contact holes for the memorycell lower contact electrodes are filled up with the high resistivemetal film 20, however, use may be made of a metal film excellent in CMPplanarization characteristics, capable of planarizing the upper surfacesof the memory cell lower contact electrodes. For example, Mo(molybdenum) small in grain size may be used. Metal excellent in CMPplanarization characteristics has an advantageous effect of suppressinglocalized phase change due to electric field concentration occurring touneven portions of contact metal.

As a result, a memory cell element is improved in respect of uniformityin electric characteristics, reliability in the number of refresh times,and high-temperature resistant operation characteristics.

Subsequently, the phase change recording material film 22, the phasechange recording material film 23 having, for example, a melting pointdifferent from that of the phase change recording material film 22, andthe metal film 24, made of, for example, tungsten, are deposited in thatorder, whereupon a structure as shown in FIG. 13 is formed.

Thereafter, the phase-shift-material-peel-preventive film 21, the phasechange recording material film 22, the phase change recording materialfilm 23, and the tungsten film 24 are worked into the resistor elementR, whereupon a structure as shown in FIG. 14 is formed.

Subsequently, the inter-level insulation film 11 e is deposited thereon,whereupon a structure as shown in FIG. 15 is formed.

Subsequently, by the lithographic and dry etching processes, the contacthole is bored in the inter-level insulation film 11 e of the memory cellarea mmry, and in the inter-level insulation film 11 e of the logiccircuit area lgc, respectively, and the barrier metal film 25 andtungsten film 26 are deposited in that order. These contact hole arefilled up and etch back is applied until the upper surface of theinter-level insulation film 11 e is exposed and the respective uppersurfaces of the tungsten films 26, 25 a in the contact holes are flushwith the upper surface of the inter-level insulation film 11 e, therebycompletely isolating an electrode contact in the via VM in the memorycell area from an electrode contact in the via VL in the logic circuitarea, whereupon a structure as shown in FIG. 16 is formed.

Thereafter, a copper interconnect barrier film 27 and the inter-levelinsulation film 11 f are deposited on the surface, interconnect groovesare cut in the inter-level insulation film 11 f by the lithographic anddry etching processes, a copper interconnect 29 and copper interconnectmetal barrier film 29 are deposited in that order, the interconnectgrooves are filled up, and etch back is applied until the upper surfaceof the inter-level insulation film 11 f is exposed and the upper surfaceof the metal interconnect in the interconnect grooves is flush with theupper surface of the inter-level insulation film 11 f, thereby formingthe second layer interconnect M2, whereupon a structure as shown in FIG.17 is formed.

In the upper part of the second layer interconnect M2, a plurality ofinterconnect layers are formed by use of the public known method,however, those interconnect layers are not shown in the figure.

Further, by use of the public known method, hydrogen annealing at atemperature on the order of 400 to 450° C. is applied before completionof the semiconductor integrated circuit device.

Further, with the present embodiment, as shown in FIG. 2, the elementactive areas are of a straight line type in shape, and the bit linecontact electrodes BC are formed so as to be protruded along thelongitudinal direction of the element active areas, however, as shown inFIG. 18, the element active areas may be of a protruded type in shape.

Furthermore, as shown in FIGS. 19 and 20, the element active areas maybe of an oblique type in shape, against the respective bit lines. Stillfurther, the element active areas may be of a straight line type inshape as shown in FIG. 47.

Yet further, with the present embodiment, as shown in FIG. 3, afolded-bit-line-layout, or a so-called two-intersecting point layout isadopted whereby the memory cell elements are arranged so as to bedisposed in the direction of the word lines at a frequency of once everytwo cycles of bit line cycles. The layout is advantageous in that thememory cell elements in close proximity to each other are not selectedso as to use the same word line, so that mutual action between thememory cells in close proximity to each other can be suppressed.

Further, as shown FIGS. 21, and 22, an open-bit-line-layout, or aso-called one-intersecting point layout may be adopted whereby thememory cell elements are arranged so as to be disposed in the directionof the word line at a frequency of once every cycle of the bit linecycles. The layout is advantageous in that the memory cells can behighly integrated.

Still further, as shown FIGS. 23, and 24, an open-bit-line-layout, or aso-called 1.5 intersecting point layout may be adopted whereby thememory cell elements are arranged so as to be disposed in the directionof the word line at a frequency of twice every three cycles of the bitline cycles.

With Embodiment 1, the phase change material layer is for common use,and an interface between the upper part of the memory cell lower contactelectrode TP and the phase-shift-material-peel-preventive film 21 is asshown in FIG. 27.

With the memory cell element in the high resistance state (“1” state), aphase change material turns into an amorphous sate in such a way as tocover the upper surface of each of the memory cell lower contactelectrodes as shown in FIG. 39. In contrast, with the memory cellelement in the low resistance state (“0” state), the phase changematerial in its entirety turns into a crystallized state as shown inFIG. 40.

Further, with the memory cell element in the high resistance state (“1”state), the phase change material in its entirety may be in an amorphoussate as shown in FIG. 41. In contrast, with the memory cell element inthe low resistance state (“0” state), the phase change material turnsinto a crystallized state in such a way as to cover the upper surface ofeach of the memory cell lower contact electrodes TP as shown in FIG. 42.

In this connection, in FIGS. 41 and 42, the phase change material layeris assumed to be a single layer, but the same may be a stacked layer.

Thus, with the present embodiment, the phase change material layer isfor common use in the memory cell area where the memory cell elementsare disposed so as to be integrated. As a result, electricalcharacteristics of the memory cell elements become uniform, therebyenabling reliability to be enhanced.

The reason why such an advantageous effect can be obtained is describedin detail hereinafter.

An assumption is made that a sectional view of the principal parts of asemiconductor integrated circuit device is, for example, as shown inFIG. 48. With the semiconductor integrated circuit device in FIG. 48,the bit lines BL2 are disposed above phase change material layers. Inthe case of this example, the sidewalls of the respective phase changematerial layers are disposed so as to be exposed for every memory cellelement. Accordingly, an effect of etching on the shape of the memorycell elements and variation in the composition thereof results.

With the present embodiment, however, since no sidewall interface of thephase change material layer exists except for the memory cell elementspositioned at the outermost peripheral parts of the memory cell area,the effect of etching on the shapes of the memory cell elements andvariation in the composition thereof is eliminated.

That is, the reason for obtaining the advantageous effect is that thesidewall interface of the phase change material layer except for thememory cell elements positioned at the outermost peripheral parts of thememory cell area can be eliminated and the effect of the etching on theshapes of the memory cell elements and variation in the compositionthereof is eliminated.

Further, with the present embodiment, the phase change material layer isa stacked layer made up of the phase change recording material filmsdiffering in property from each other, particularly, a stacked layer ofhigh-melting phase change recording material film and low-melting phasechange recording material film. As a result, the electricalcharacteristics of the memory cell elements become uniform, therebyenabling reliability thereof to be enhanced.

The reason for obtaining the advantageous effect described is describedin further detail hereinafter. If the phase change recording materialfilm in contact with the memory cell upper plate electrode has a meltingpoint higher than that for the other phase change recording materialfilm formed underneath the phase change recording material film, anamorphous layer can cause phase change to occur such that a phase changearea of the phase change material layer is reduced in shape,particularly, along a direction in which the phase change recordingmaterial films are stacked. For example, as shown in FIG. 39, it ispossible to prevent the amorphous layer formed from the memory celllower contact electrode from coming in contact with the memory cellupper plate electrode. As a result, mutual diffusion of metallicsubstances between the phase change material layer and the memory cellupper plate electrode can be prevented, so that it has become possibleto ensure uniformity in the electrical characteristics of the memorycell elements, thereby enabling reliability thereof to be enhanced.

Further, with the present embodiment, the high resistive conductivematerial is disposed only in the upper part of each of the memory celllower contact electrodes connecting the phase change material layer tothe metal contact electrodes connected with the respective active areason the semiconductor substrate, for the MISFETs. As a result, the upperpart of each of the memory cell lower contact electrodes can serve as aheater generating Joule heat, so that refresh speed of the respectivememory cell elements can be enhanced.

The reason why such an advantageous effect can be obtained is describedin detail hereinafter. If the high resistive conductive material is notdisposed in the upper part of each of the memory cell lower contactelectrodes, heat is prone to escape from the phase change material layerto the memory cell lower contact electrodes when heating the phasechange material layer by use of electric pulses. For this reason,temperature at portions of the phase change material layer, in closeproximity to the respective memory cell lower contact electrodes, drops,so that it is not possible to cause phase change to occur such that thephase change area of the phase change material layer changes in shape,particularly, areas thereof, in close proximity to the respective memorycell lower contact electrodes, change in shape so as to completely coverthe upper surface of each of the memory cell lower contact electrodes asshown in FIG. 40. However, if the high resistive conductive material isdisposed only in the upper part of each of the memory cell lower contactelectrodes, the high resistive conductive material generates Joule heat,so that heat to the memory cell lower contact electrodes is lessconducted, thereby checking a drop in temperature at the portions of thephase change material layer, in close proximity to the respective memorycell lower contact electrodes. As a result, within short time, the phasechange material can completely cover the upper surface of each of thememory cell lower contact electrodes, particularly in the phase changearea in close proximity to a contact part between the memory cell lowercontact electrodes and the phase change material layer, as shown in FIG.39.

Furthermore, if the high resistive conductive material is disposedthroughout each of the memory cell lower contact electrodes, aresistance value of each of the memory cell lower contact electrodesbecomes high, thereby creating a cause for deterioration in operatingcharacteristics of the memory. On the other hand, if the high resistiveconductive material is disposed only in the upper part of each of thememory cell lower contact electrodes, the resistance value thereofhardly changes.

Further, with the present embodiment, the phase change material layer isprovided for common use in the memory cell area where the memory cellelements are disposed so as to be integrated, and further, the commonupper metal electrode connected to a power source line is formed only inthe upper layer of the phase change material layer. As a result,electrical characteristics of the memory cell elements become uniform,thereby enabling reliability thereof to be enhanced.

The reason for obtaining such an advantageous effect is described indetail hereinafter. If the common upper metal electrode 24 is formedonly in the upper layer of the phase change material layer, electricfields in the lateral direction in FIG. 43 can be checked, so that aninteraction between the phase change memories adjacent to each other canbe checked, thereby enabling uniformity of electrical characteristics ofthe memory cell elements to be ensured and reliability thereof to beenhanced.

However, if an electrode 31 is formed at sidewalls of the phase changematerial layer, respectively, as shown in FIG. 44, electric fields inthe lateral direction in FIG. 44 are generated as main constituents,thereby raising a possibility of an interaction occurring between thephase change memories adjacent to each other.

Further, with the present embodiment, a contact electrode connecting thephase change material layer with the diffusion layer of the MISFET is atwo-stage contact electrode. As a result, while optimizing the structureof the memory cell lower contact electrode, that is, the upper stage ofthe two-stage plug electrode, for enhancement of the characteristics ofthe phase change memory, the metal contact electrode, that is, the lowerstage of the two-stage plug electrode, along with the bit line contactelectrodes and the MISFETs in the logic circuit area, are formed by aconcurrent process, thereby enabling low cost to be achieved.

Still further, with the present embodiment, the bit lines are disposedunder the phase change material layer. As a result, uniformity in theelectrical characteristics of the memory cell elements is achieved,thereby enabling reliability thereof to be enhanced.

The reason for obtaining such an advantageous effect is described indetail hereinafter. When the bit lines are disposed under the phasechange material layer, the bit line contact electrode is disposedbetween the respective bit lines and the semiconductor area DNC of therespective MISFETs for selection of the memory cell. That is, the bitline contact electrode neither penetrates through the phase changematerial layer, nor is disposed within the phase change material layer.As a result, the side walls of the phase change material layer areprevented from exposure due to penetration by bit line plugs, so thatuniformity in the electrical characteristics of the memory cell elementsis achieved, thereby enabling reliability thereof to be enhanced.

Further, with the present embodiment, the hydrogen annealing at atemperature in a range of about 400 to 450° C. is applied by use of thepublic known method. Accordingly, the phase change material layer of thesemiconductor integrated circuit device as completed, in the initialcondition, is crystallized. By use of the phase change material layer ina crystallized condition, portions of the phase change material layer,in close proximity to the lower electrodes, are turned amorphous,thereby enabling the phase change memory cell to be operated.

<Embodiment 2>

The present embodiment relates to a structure wherein phase changematerial layers which chalcogenide layers and plate electrodes areseparated from each other are disposed above bit lines.

A method of fabricating a semiconductor integrated circuit deviceaccording to Embodiment 2 up to depositing aphase-shift-material-peel-preventive film 21, phase change recordingmaterial film 22, phase change recording material film 23, and tungstenfilm 24 is the same as the method of fabricating the semiconductorintegrated circuit device according to Embodiment 1 up to depositing thephase-shift-material-peel-preventive film 21 made of silicon nitride,phase change recording material film 22, phase change recording materialfilm 23, and memory cell upper plate electrode 24 made of tungsten,omitting therefore description thereof.

With the present embodiment, the phase-shift-material-peel-preventivefilm 21, phase change recording material film 22, phase change recordingmaterial film 23, and tungsten film 24 are subsequently worked intoresistor elements R, whereupon a structure as shown in FIG. 25 isformed.

A fabricating method thereafter is the same as that according toEmbodiment 1, and a structure after the formation of a second layerinterconnect is as shown in FIG. 26.

With the present embodiment, the resistor elements R are separated fromeach other by the memory cell element as shown in FIG. 28. Since the bitlines BL are disposed under the phase change material layer, the memorycell elements can be disposed without being affected by disposition ofthe bit lines and bit line plugs, so that high integration of a memorycell can be achieved by suppressing area penalty for the sake ofuniformity in the electrical characteristics of the memory cellelements, and enhancement in reliability of the memory cell elements.

Further, with the present embodiment, the phase change material layersare separated from each other by the memory cell element, however, asshown in FIG. 29, the phase change material layers may be separated fromeach other by the bit line cycle. This shape can be rendered to be anoptional shape without area penalty due to the effects of through-holesfor bit line contact electrodes.

Still further, as shown in FIG. 30, the phase change material layers maybe separated from each other by the word line cycle. This shape can berendered to be an optional shape without the area penalty due to theeffects of the through-holes for the bit line contact electrodes.

Yet further, as shown in FIG. 31, the phase change material layers maybe separated from each other by the element active area cycle. Thisshape can be rendered to be an optional shape without the area penaltydue to the effects of the through-holes for the bit line contactelectrodes.

Further, with the present embodiment, the memory cell upper plateelectrodes are disposed on top of the phase change material layers,respectively, however, as shown in FIG. 45, a structure may be adoptedwherein the second layer interconnect is disposed by connecting thephase change materials with vias VM in a memory cell area, respectively.With the use of copper. wiring for the second layer interconnect, theupper plate electrodes can be rendered lower in resistance.

<Embodiment 3>

The present embodiment relates to a structure wherein a common plateelectrode is disposed in the upper part of a phase change materiallayers which chalcogenide layers are separated from each other.

A method of fabricating a semiconductor integrated circuit deviceaccording to Embodiment 3, up to the steps of depositing a highresistive metal film 20, made up of, for example, a titanium film andtitanium nitride film, in that order from a lower layer, by thesputtering process and so forth, to be embedded in respective contactholes, etching back the high resistive metal film 20 until the uppersurface of a phase-shift-material-peel-preventive film 21 is exposed,and the upper surface of each of memory cell lower contact electrodes TPin the respective contact holes is flush with that of thephase-shift-material-peel-preventive film 21, and completely isolatingthe respective memory cell lower contact electrodes TP from each otheris the same as the fabricating method according to Embodiment 1,comprising the steps of depositing the high resistive metal film 20,made up of the titanium film and titanium nitride film, in that orderfrom the lower layer, by the sputtering process and so forth, to beembedded in the respective contact holes, etching back the highresistive metal film 20 until the upper surface of thephase-shift-material-peel-preventive film 21 is exposed, and the uppersurface of each of the memory cell lower contact electrodes TP in therespective contact holes is flush with that of thephase-shift-material-peel-preventive film 21, and completely isolatingthe respective memory cell lower contact electrodes TP from each other,as shown in FIGS. 4 through 12, omitting therefore description thereof.

With the present embodiment, the phase-shift-material-peel-preventivefilm 21, a phase change recording material film 22, and a phase changerecording material film 23, are subsequently deposited, whereupon astructure as shown in FIG. 32 is formed.

Subsequently, the phase-shift-material-peel-preventive film 21, phasechange recording material film 22, and phase change recording materialfilm 23, are worked into the phase change material layers CG, whereupona structure as shown in FIG. 33 is formed.

Subsequently, an inter-level film 11 g is deposited, and the uppersurface of the phase change material layer is exposed by etching backthe inter-level film 11 g by use of, for example, the CMP, whereupon astructure as shown in FIG. 34 is formed.

Then, for example, a tungsten film 24 is deposited, whereupon astructure as shown in FIG. 35 is formed.

Subsequently, the tungsten film 24 is worked into a memory cell upperplate electrode, whereupon a structure as shown in FIG. 36 is formed.

Subsequently, an inter-level film 11 h is deposited, whereupon astructure as shown in FIG. 37 is formed.

A fabricating method thereafter is the same as that in the case ofEmbodiment 1, and after a second layer interconnect is formed, astructure becomes as shown in FIG. 38.

With the present embodiment, the upper plate electrode is formed on thephase change material layers. In the case of the upper plate electrodesharing a plurality of the phase change material layers in order todispose a bit line under the respective phase change material layers,memory cells can be disposed without being affected by disposition ofthe bit lines and bit line plugs, so that high integration of a memorycell can be achieved by suppressing area penalty for the sake ofuniformity in the electrical characteristics of the memory cellelements, and enhancement in reliability of the memory cell elements.

Further, with the present embodiment, as shown in a layout view of theprincipal parts of respective interfaces between the phase changematerial layers and the memory cell upper plate electrode, in FIG. 46,the memory cell upper plate electrode 32 may be divided so as to inparallel with the respective bit lines.

Still further, with the present embodiment, the memory cell upper plateelectrode may be divided in an optional shape provided that the same isin contact with the upper surface of the respective phase changematerial layers serving as the respective memory cell elements, having asufficient contact area.

<Embodiment 4>

The present embodiment relates to a structure wherein a bit line layeris stacked on top of a resistor element, and the bit line layer asstacked is separated along the direction of word lines, in other word,is disposed so as not to be separated along the direction of bit lines.

A method of fabricating a semiconductor integrated circuit deviceaccording to Embodiment 4, up to the steps of depositing aphase-shift-material-peel-preventive film 21, phase change recordingmaterial film 22, phase change recording material film 23, and tungstenfilm 24BL is the same as the fabricating method according to Embodiment1, comprising the steps of depositing thephase-shift-material-peel-preventive film 21 made of silicon nitride,phase change recording material film 22, phase change recording materialfilm 23, and memory cell upper plate electrode 24 made of tungsten, asshown in FIGS. 4 through 13, omitting therefore description thereof.Subsequently, with present embodiment, thephase-shift-material-peel-preventive-film 21, phase change recordingmaterial 23, and tungsten film 24BL are worked into a stacked layer RBLof the resistor element and the bit line layer, whereupon a structure asshown in FIG. 49 is formed. A fabrication method thereafter is the sameas that according to Embodiment 1.

With present embodiment, the tungsten film 24BL serves as the bit lines.The bit lines are stacked on top of the resistor element, that is, aredisposed on top of the resistor element. Further, a first layerinterconnect M1 disposed under the resistor element does not serve asthe bit lines, but serves as, for example, ground wiring.

With present embodiment, the phase change material layer is divided bythe bit line cycle as shown FIG. 51. This shape enables high integrationof a memory cell by suppressing area penalty for the sake of uniformityin the electrical characteristics of memory cell elements, andenhancement in reliability of the memory cell elements owing to theeffect that sidewalls of the phase change material layer as divided arenot exposed in the direction of the bit lines.

Further, with present embodiment, by adopting a two-intersecting pointcell disposition for element active areas as shown in FIG. 18, a stackedlayer RBL of the resistor element and the bit line layer may be dividedonce every two bit lines so that the element active areas adjacent toeach other are not selected by the same word line. In this case, alayout of disposition of the stacked layer RBL of the resistor elementand the bit line layer against plugs of memory cell lower contactelectrodes is as shown in FIG. 50. In this connection, with the adoptionof the two-intersecting point cell disposition for the element activeareas as shown in FIG. 18, memory cells are disposed such that thememory cells adjacent to each other, on the same word line, are notselected by the respective bit lines shown in FIG. 50. With presentembodiment, since the phase change material layer including the uppermetal electrode are used as the bit lines, the sidewalls of the phasechange material layer as divided are not exposed in the direction of thebit lines and between two of the bit lines, not selected by the sameword line, thereby enables high integration of a memory cell bysuppressing area penalty for the sake of uniformity in the electricalcharacteristics of memory cell elements, and enhancement in reliabilityof the memory cell elements.

As described in the foregoing, the invention developed by the inventorhas been specifically described with reference to the embodimentsthereof, however, it goes without saying that the invention is notlimited thereto, and various modifications may be made therein withoutdeparting from the spirit and scope of the invention.

Advantageous effects obtained by representative embodiments of theinvention as disclosed by the present application are broadly describedas follows.

By providing the phase change material layer for common use and formingthe plate electrode in the upper part thereof, it becomes possible tosuppress lack of uniformity in electrical characteristics of a phasechange memory, and deterioration in reliability thereof, due to workingon the phase change material layer.

Further, by disposing the high resistive conductive material only in theupper part of each of the contact electrodes connecting the phase changematerial layer with the semiconductor areas of the MISFETs for selectionof the memory cell, in other word, by disposing the high resistiveconductive material such that portions of the contact electrodes, incontact with the phase change material layer, only act as the heatersgenerating Joule heat, formation of the phase change areas is speeded upand the refresh speed of the respective memory cell elements can beenhanced.

Further, since the phase change material layer is disposed above the bitlines, the memory cell elements can be disposed at high integration bysuppressing the area penalty without being affected by the bit linecontact electrodes, so that the phase change memory can be mountedjointly with the logic in the semiconductor integrated circuit device byuse a process having affinity for the system-on-chip process.

1. A semiconductor integrated circuit device having a plurality ofmemory cells formed on a semiconductor substrate, each made up byelectrically connecting a resistor element in series with a field effecttransistor; the resistor element comprising stacked layer films formedof a first electrode layer, a phase change material layer made of onephase change material layer or plural phase change material layers withresistance values changing by heating treatments, and a second electrodelayer, deposited in that order, and connected to a power source terminalcommon to the respective field effect transistors in at least two of thememory cells.
 2. A semiconductor integrated circuit device comprising aplurality of memory cells formed on a semiconductor substrate, each madeup by electrically connecting a resistor element in series with a fieldeffect transistor; the field effect transistor having either of a sourceand a drain, connected to a conductive film serving as bit lines of thememory cells, respectively, and the other of the source and the drain,connected to the resistor element; the resistor element comprisingstacked layer films made up of a first electrode layer, a phase changematerial layer made of one phase change material layer or plural phasechange material layers with resistance values changing by heatingtreatments, and a second electrode layer, deposited in that order, andbeing formed on the conductive film through the intermediary of aninsulation film so as to be connected in common to the other of thesource and the drain, in at least two of the memory cells.
 3. Asemiconductor integrated circuit device comprising a plurality of memorycells formed on a semiconductor substrate, each made up by electricallyconnecting a resistor element in series with a field effect transistor;the field effect transistor having either of a source and a drain,connected to a conductive film serving as bit lines of the memory cells,respectively, and the other of the source and the drain, connected tothe resistor element; the resistor element comprising stacked layerfilms made up of a first electrode layer, a phase change material layermade of one phase change material layer or plural phase change materiallayers with resistance values changing by heating treatments, and asecond electrode layer, deposited in that order, and formed on theconductive film through the intermediary of an insulation film so as tobe individually connected to the respective field effect transistors inthe memory cells.
 4. A semiconductor integrated circuit devicecomprising a plurality of memory cells formed on a semiconductorsubstrate, each made up by electrically connecting a resistor element inseries with a field effect transistor; the field effect transistorhaving either of a source and a drain, connected to a conductive filmserving as bit lines of the memory cells, respectively, and the other ofthe source and the drain, connected to the resistor element; theresistor element comprising stacked layer films made up of a firstelectrode layer, a phase change material layer made of one phase changematerial layer or plural phase change material layers with resistancevalues changing by heating treatments, and a second electrode layer,deposited in that order, formed on the conductive film through theintermediary of an insulation film and configured such that the firstelectrode layer and the phase change material layer are divided by thememory cell and the second electrode layer is connected to a powersource terminal common to the respective field effect transistors in atleast two of the memory cells.
 5. A semiconductor integrated circuitdevice according to claim 1, wherein either of a source and a drain, inthe field effect transistor, is connected to the first electrode layerwith a plug layer made up by filling up a contact hole, formed in aninsulation film, with a conductive material.
 6. A semiconductorintegrated circuit device according to claim 5, wherein the plug layercomprises a first plug layer connecting the other of the source and thedrain, in the field effect transistor, with the bit lines, and a secondplug layer extended on the first plug layer and connected to the firstelectrode layer.
 7. A semiconductor integrated circuit device accordingto claim 6, wherein the second plug layer is smaller in cross sectionalarea than the first plug layer.
 8. A semiconductor integrated circuitdevice according to claim 6, wherein the second plug layer has aninsulation thin film deposited along an inner peripheral sidewall of thecontact hole.
 9. A semiconductor integrated circuit device according toclaim 6, wherein the second plug layer comprises a first conductivelayer having a first resistance value and a second conductive layerhaving a resistance value higher than the first resistance value, andthe second conductive layer is connected to the phase change materiallayer.
 10. A semiconductor integrated circuit device according to claim1, wherein the phase change material layer comprises stacked layer filmsformed of a first phase change material layer made of a first meltingpoint material, and a second phase change material layer made of amaterial having a melting point higher than that of the first meltingpoint material layer, deposited in that order, and the first phasechange material layer is connected to either of the source and thedrain, in the field effect transistor.
 11. A semiconductor integratedcircuit device according to claim 1, wherein the phase change materiallayer comprises a first phase change material layer in a crystallizedstate.
 12. A semiconductor integrated circuit device according to claim1, wherein the phase change material layer comprises a second phasechange material layer in an amorphous state.
 13. A semiconductorintegrated circuit device according to claim 1, wherein the phase changematerial layer comprises stacked layer films formed of a first phasechange material layer in a crystallized state, and a second phase changematerial layer in an amorphous state, deposited in that order, and thefirst phase change material layer is connected to either of the sourceand the drain, in the field effect transistor.
 14. A semiconductorintegrated circuit device according to claim 1, wherein the phase changematerial layer comprises stacked layer films formed of a first phasechange material layer in an amorphous state, and a second phase changematerial layer in a crystallized state, deposited in that order, and thefirst phase change material layer is connected to either of the sourceand the drain, in the field effect transistor.
 15. A semiconductorintegrated circuit device according to claim 1, wherein the phase changematerial layer comprises stacked layer films formed of a first phasechange material layer in an amorphous state, and a second phase changematerial layer in a crystallized state, deposited in that order, and thefirst phase change material layer is connected to either of the sourceand the drain, in the field effect transistor, with a plug layer formedin a insulation film, having an area where a portion of the first phasechange material layer is crystallized due to Joule heat generated byflow of current to the plug layer.
 16. A semiconductor integratedcircuit device according to claim 1, wherein any material selected fromthe group consisting of TiN, TiAlN, and PolySi is provided in a portionof the second plug layer, connected to the resistor element.
 17. Asemiconductor integrated circuit device according to claim 1, wherein amolybdenum material is provided in a portion of the second plug layer,connected to the resistor element.
 18. A semiconductor integratedcircuit device comprising a plurality of memory cells formed on asemiconductor substrate, each made up by electrically connecting aresistor element in series with a field effect transistor; the fieldeffect transistor having either of a source and a drain, connected tothe resistor element; the resistor element comprising stacked layerfilms made up of a first electrode layer, a phase change material layermade of one phase change material layer or plural phase change materiallayers with resistance values changing by heating treatments, and asecond electrode layer, deposited in that order; the second electrodelayer deposited on the phase change material layer of the stacked layerfilms, serving as bit lines, and being configured so as to be connectedin common to the other of the source and the drain, in at least two ofthe memory cells.